The company, which operates the massive Caremark pharmacy benefits manager as well as the CVS drugstore chain, has offered more than $200 a share, according to the WSJ. The news sent Aetna shares up 12% to $180.70, showing that the markets find the news credible. CVS’ shares slipped 3%, presumably on concerns of how such a large transaction would be financed. CVS’ stock market value is about $75 billion.

A CVS spokesperson declined to comment citing company policy on market speculation, while Aetna could not immediately be reached for comment.

While CVS is best known for its namesake drugstores, its Caremark is the second largest PBM in the country after Express Scripts esrx and processes prescription-drug programs for big companies and health insurers, representing tens of millions of people.

CVS, which bought Caremark in 2007 for $21 billion, has made a number of deals in recent years to beef up both its retail and its PBM business, which are meant to feed business to each other. In 2015, it bought Target’s tgt pharmacy business and has hundreds of stores within the discount store. In the last few years, on CVS Health CEO Larry Merlo’s watch, the company has also bought Coram, which delivers treatments to homebound patients, for $2 billion, teamed up with Cardinal Health to create the largest U.S. generic-drug purchasing operation, Red Oak Sourcing, and in 2015, paid $12.7 billion for Omnicare, a distributor of prescription drugs to nursing homes and assisted-living facilities.